The present invention relates to a glue stick with an outer sleeve open at least at one side, for receiving a rod-like adhesive mass, in said glue stick there being located a threaded spindle which is connected to a rotary cap arranged on one side and being in interactive connection with the spindle.
Glue sticks of this type are on the market and hardly differ in shape and size independently of the manufacturer. For example here in particular the documents DE1511732B, DE1921937U, DE2139123B or U.S. Pat. No. 2,935,191A are referred to.
On the market there are offered glue sticks above all in three formats, with a filled weight of the adhesive mass of approx. 10 grams, 20 grams or 40 grams. The rod-like adhesive mass at the same time is located in the outer sleeve whose inner diameter corresponds to the diameter of the rod-like adhesive mass located therein. The inner diameter of the smaller outer sleeve measures usually about 15 millimeters, the inner diameter of the outer sleeve of the larger variant between 19-24 millimeters. The length of the outer sleeve, which is available for receiving the rod-like adhesive mass is about 40-45 millimeters, whilst the corresponding length with the larger outer sleeve is about 50-65 millimeters. With the glue sticks common today which are obtainable on the market the ratio of the inner diameter of the outer sleeve to the length of the part of the outer sleeve which serves for receiving the rod-like adhesive mass is thus about 1:3. This ratio is on the one hand caused by the consistency of the adhesive mass and on the other hand by the design principle applied up to today. The stunted shape of the glue sticks, that is to say relatively thick and relatively short renders the glue stick unsuitable for its portability and keeping, similar to a ball-point pen or ink pen or other writing utensils. Normally they are kept standing or lying on a table surface. Accordingly the rotary caps form the standing surfaces of the glue sticks.
On account of the shape therefore also small adhesive surfaces are very difficult to be coated with these glue sticks.
As already mentioned the shaping of the outer sleeve is essentially dependent on the consistency of the adhesive mass and the design principle of the glue sticks. The rod-like adhesive mass is on the one hand held in a receiving holder which is part of a piston which by way of a threaded spindle in the outer sleeve is movable up and down. The adhesive mass at the same time contacts the outer sleeve and corresponding adhesion forces occur. Whilst the expulsion of the rod-like adhesive mass is basically also possible with a longer outer sleeve, however the retraction of the rod-like adhesive masses causes a problem. With this the rod-like adhesive mass may be pulled out of the receiving holder of the piston so that the glue stick may no longer be retracted. This may be partly solved technically in that one provides the receiving holder with more heavily projecting radially inwardly directed ribs, but then there still remains a problem. With a larger length or with a ratio of the inner diameter of the outer sleeve to the length of the part of the outer sleeve which serves for receiving a rod-like adhesive mass which is larger than 1:3, thus for example 1:5 or even higher, the rod-like adhesive mass is inevitably separated, that is to say a part is retracted with the receiving holder of the piston, whilst the upper part is no longer transported. Although thus already for many years there has existed a demand for long, thin glue sticks in the configuration shape of pens, until today one has not succeeded in offering such glue sticks.
It is therefore the object of the present invention to provide a glue stick of the initially mentioned type which is relatively long and relatively thin and has roughly the dimensions of a writing pen without at the same time the mentioned problems occuring.
This object is achieved with a glue stick with the features of an outer sleeve open at least on a first end of the glue stick, for receiving a rod-like adhesive mass; a threaded spindle connected to a rotary cap which is arranged on a second end of the glue stick and which is in interactive connection with the threaded spindle; and a piston running on the threaded spindle and which with respect to the outer sleeve is rotationally secured so that a rotary actuation of the rotary cap effects an axial displacement of the piston. The ratio of the inner diameter (Ad) of the outer sleeve to the length (AL) of a part of the outer sleeve which serves for receiving the rod-like adhesive mass lies in the region of 1:6 to 1:15. Thanks to the special shaping of the threaded spindle which here carries out a double function, specifically on the one hand the conventional function as a screw member for moving the piston and on the other hand in that the threaded spindle simultaneously is configured as a conveyor worm, the rod-like adhesive mass is actuated from the inside practically over the whole length.
In principle the threaded spindle or conveyor worm may have various embodiment forms. With the considerably longer configuration of the threaded spindle as a conveyor worm one must however take into account the fact that the adhesion forces with larger lengths of the rod-like adhesive mass increase in a relative manner. At the same time there exists the danger of a bending or even bending-breakage of the threaded spindle. In order to avoid this, it is advantageous to shape the threaded spindle such that the ratio of spindle core diameter to spindle inner diameter lies above 1:1.5, preferably between 1:1.8 and 1:3. In order to achieve favorable transport conditions it is advantageous to select the ratio of the thread depth of the threaded spindle to the inner radius of the outer sleeve between 1:3 to 1:10 in order to achieve a suitable perfect transport.
Furthermore it has been shown to be advantageous to configure the piston which runs on the threaded spindle with a receiving holder on the adhesive side and on the side of the rotary cap with a threaded sleeve. This threaded sleeve may thanks to a suitable length serve to stabilize the threaded spindle from bending-breakage. Preferably this is achieved when the length of the threaded sleeve is at least approximately three to six times the nominal diameter of the threaded spindle.
Further advantageous embodiment forms and their significance and manner of acting inasmuch as they have not yet been explained, are to be deduced from the subsequent description.